Common parallel negative feedback amplifiers

Common parallel negative feedback amplifiers

(I) Parallel negative feedback amplifier
    The figure shows a common parallel negative feedback amplifier. The resistor R is a voltage negative feedback element . The left end of the resistor R is directly
connected to the input end, and the right end is directly connected to the output end, linking the input and input circuits.
    First, assume that a certain instantaneous input signal is positive (+). Since the voltage polarity output by the common-emitter transistor amplifier is opposite to that of the input,
it is negative C-). Through the feedback element R, the negative-polarity feedback signal is added to the base ( b). The assumed polarity of the signal source is opposite, which reduces the voltage,
so the feedback element R is negative feedback. Then, short-circuit the output end of the amplifier to ground, and the collector of the transistor through capacitor C2 will be AC ​​grounded
. At this time, no signal will be fed back to the base of the transistor through the negative feedback element R, and there will be no negative feedback signal in the circuit. , so this is
a voltage negative feedback circuit.